This present invention relates to a locking device to be installed on and removed from a brace, or strut in the framework of a scaffold.
Generally, framework scaffolds are built at a work site of a building, shipbuilding, civil works, or the like, and braces and handrails are provided on the struts of the frame side, when workers are to walk on the scaffold, to maintain safety and prevent tools and broken pieces from falling during work. In the conventional method, when securing such braces and handrails onto the frame side, a locking device called a gravity lock is projectively provided in the frame side strut and the holes provided in the brace, etc. are inserted in this locking device.
In a conventional locking device of this kind, a pipeform body or bar-form body is known and used with a stopping piece which drops, but its own weight, and is pinned swingably to the body.
In this case, the locking device having a pipe-like body is hollow and its strength is weak due to a small thickness of the tube. The tube body tends to bend or become dented when hit by other object with a resultant unsmooth swinging of the stopping piece. While the pipe-like lock device generally incorporates a spring inside, to control the movement in the stopping piece. As a result, its construction is complicated, working involves difficulty, dust enters, the movement of the stopping piece is hindered when seized due to rust and the spring tension is lost after repeated use for a long time which lowers it durability.
On the other hand, the lock device having a round bar-like body, for example, ones that having the construction as shown in FIG. 1(a) and (b), is designed so that groove 2 of any desired width is cut from the front end of bar body 1 through the center. The end of stopping piece 3 is swingably attached via rivets 4 and 5 in the groove 2. One rivet 5 is inserted in hole 6 of stopping piece 3 and stopping piece 3 moves within the range of the inside diameter of this hole 6. Stopping piece 3 descends due to its own weight when the brace is inserted into the body 1 and the stop face 7 in the rear part thereof prevents the brace from taken off.
An other example of a conventional bar-like body locking device, those shown in FIG. 2(a) and (b) are known. These are designed so that groove 9 is cut from the front end of body 8 toward the center. At nearly the center of stopping piece 10, it is rotatably supported in groove 2 via rivet 11, and stopping piece 10 turns by its own weight as the brace is inserted onto body 8 and becomes vertical as shown, thus preventing the brace from being taken off.
In the above conventional locking devices, for inserting and removing the brace, stopping pieces 3 and 10 must be pushed into grooves 2 so that one can 9 by finger tip and bring bodies 1 and 8 into their horizontal position.
The body of the above-mentioned bar-like locking device is stronger than the pipe-like locking device. It has, however, disadvantages due to grooves 2 and 9 being cut from the front end. These are as follows: (1) the body is less durable, in particularly the front end tends to be broken with a resultant hindered of movement of stopping pieces 3 and 10 thereby further making removal and installation of the brace; (2) the front end of the body tends to be narrowed due to force applied from each end of rivets 4 and 11 when rivets for holding stopping pieces 3 and 10 are caulked causing possible stopping of movement of stopping pieces 3 and 10, fabrication so as not to narrow the width is difficult, and workability is low; (3) that dust and water tend to enter grooves 2 and 9 during work and due to various reasons since the tops of grooves 2 and 9 are not covered, dust may be caught between grooves 2, 9 and stopping piece 3, 10 thereby stopping the movement of stopping piece 3, 10 causing water collection with resltant rust generation; (4) that in the construction such as FIG. 1 two rivets 4 and 5 are required and hole 6 must be drilled thus making work very difficult with resultant high cost; and (5) that in the construction as shown in FIG. 2, for inserting the brace it must be adjusted horizontal manually, making handling inconvenient, etc.